This project aims at testing and developing tracer techniques for their application in the monitoring of CO2 migration and storage in geological formations.
Tracers are substances that are injected in the reservoir to calibrate and validate the predictive models. Tracer technology is an effective tool to understand the flow characteristics of the injected fluid in the reservoir, to improve reservoir description and to assess the potential leakage of CO2.
In order to monitor CO2 migration and storage in geological layers, traces were used in two test sites:
- K12-B (North Sea, The Netherlands), where CO2 is used for enhanced gas recovery combined with CO2 storage;
- Ketzin (NE Germany), where CO2 is injected into an aquifer.
K12-B
Traces were added to the injected CO2 for a defined period to generate a pulse which travels from the injection well to the production well. Since the injected CO2 originates from the reservoir, a tracer substance was needed to enable monitoring of any breakthrough of injected CO2 into one of the two methane production wells and to discriminate it from resident CO2. Weekly sampling took place at the two producers K12-B1 and K12-B5, which are located at different distance from the injector. The tracers are expected to allow an accurate assessment of the flow behaviour in the reservoir and of the associated sweep efficiency of the injected CO2. Measured breakthrough data of both tracers at K12-B1 and K12-B5 showed breakthrough after around 130 and 463 days, respectively. The measurements of the tracers in both producers prove that the injected tracers have reached the producers. The tracer experiment at K12B has now been going on for almost four years and the obtained field data will serve as input for reservoir modelling for better understanding of the flow and behaviour of CO2 in a depleted gas reservoir.
Ketzin
The aim of the project was to demonstrate that tracers break through before CO2. For this, the fluids (gas and brine) in the observation wells were frequently sampled. The issue was successfully demonstrated theoretically using a numerical simulator along with a Ketzin geological model. Hence, tracers can be applied as a monitoring tool for the CO2 storage.
K12-B (North Sea, The Netherlands)
For more information please contact:
Mehran Sohrabi at Heriot-Watt University